DC brushless motor is a synchronous motor, which means that the motor rotor speed by the motor stator rotation of the magnetic field speed and the number of rotor (p):

n = 120. f / p. In the case of a fixed number of rotors, changing the frequency of the stator's rotating magnetic field can change the rotational speed of the rotor. DC brushless motor is the synchronous motor with electronic control (drive), control the stator rotation magnetic field frequency and the motor rotor speed back to the control center repeated correction, in order to achieve close to the DC motor characteristics of the way. That is, DC brushless motor can be in the rated load range when the load changes can still control the motor rotor to maintain a certain speed.

The DC brushless drive includes a power supply part and a control part. The power supply unit provides a three-phase power supply to the motor, and the control unit converts the input power frequency according to the demand.

The power supply unit can be directly DC input (usually 24v) or AC input (110v / 220v), if the input is AC must first converter (Converter) into DC. Either DC input or AC input to be transferred to the motor coil before the DC voltage from the converter (Inverter) into three-phase voltage to drive the motor. The inverter (inverter) is usually divided into upper arm (q1, q3, q5) / lower arm (q2, q4, q6) by 6 power transistors (q1 ~ q6) to connect the motor as a switch to control the flow through the motor coil. The control section provides pwm (pulse width modulation) to determine the power transistor switching frequency and converter (Inverter) commutation timing. DC brushless motor generally want to use when the load changes in the speed can be stable at the set value and will not change too much speed control, so the motor is equipped with a sensor magnetic field Hall sensor (Hall-sensor), as the speed of the Closed loop control, but also as a basis for phase control. But this is only used as a speed control and can not be used as a positioning control.